Arrow Spine Question

[Eotech]

Hey all, new to the forums but I have been following for a while. I had a quick question and I figured I could get a variety of suggestions here. I have been using Carbon Express Pile Driver Hunter 250 arrows. A friend told me that my arrow spine wasn't right for my setup. My draw length is 30" and I currently pull around 55lbs. I used a Diamond Outlaw for the first 8 months of shooting but I recently upgraded and got a Mathews Heli-m. If anyone has any recommendations or links to info that can help me out on choosing the correct spine I would greatly appreciate it. Thanks!



(Edit: Just realized I probably posted this in the wrong place but I cant find out how to move it. Sorry for the mix up.)

[Slider46]

To figure out what spine you need - check out this chart: http://www.huntersfriend.com/carbon_...deflection.htm

Choose your arrow length and point weight, find your draw length and you'll have your recommended spine.

For example - if you wanted to shoot 100grain heads with 29 arrow at 55lbs, you would want an arrow with actual deflection of 0.380" - 0.420". Carbon Express lists their actual deflection measurements on their website for each arrow so you can find an arrow with a similar spine. When in doubt - go a little stiffer. You can make adjustments to shoot a slightly overspined arrow (like increasing draw weight or head weight) but an underspined arrow is much harder to tune.

So your Piledriver 250s should be ok with your current setup. However, you could also shoot 350s and that would give you some more room to increase draw weight later on if you so choose.

Also, Carbon Express has their own "adjusted draw weight chart" here: http://www.carbonexpressarrows.com/shaft-selector

[Eotech]

Thanks, that is awesome. One more quick question. Is there a specific grain that I should go with? What determines the grain I should choose?

[Slider46]

Do you mean point/head weight?

Head weight should be determined by the arrow you want to shoot and to decide what arrow to shoot - you need to decide if you want a light but fast arrow or a slower but heavier arrow.

A light (and less stiff) arrow will work best with a lighter head (85 grain) and moderate draw weights. Advantages to a lighter arrow are increased velocity, flatter trajectory (less drop at distance). Conversely, a heavier (and stiffer) arrow will work best with a heavier head (115 or 125 grain) and higher draw weights. Advantages to a heavier arrow are more energy at longer ranges, which means more penetration at the cost of more drop at distance.

A 100 grain head with a compatible arrow shaft is a good middle ground and gives you room to play around with draw weight and arrow weight to affect velocity and kinetic energy.

This article gets pretty technical but the main point is that for hunting purposes, a heavier arrow, even though slower keeps more energy and momentum downrange and provides more penetration than a light and fast arrow. http://archeryreport.com/2011/01/hea...s-speed-power/

[Slider46]

Also remember you can't just take an arrow setup for 100 grain heads and expect to shoot 125 grain heads without affecting arrow flight. In that situation, your arrows may or may not fly correctly.

A heavier head makes the arrow act softer.
A lighter head makes the arrow act stiffer.
Shortening an arrow makes it act stiffer.
You can't lengthen a short arrow but a longer arrow will act softer.